Olefin production process

ABSTRACT

A process is provided to stabilize and/or reactivate an olefin production catalyst system which comprises contacting an olefin production catalyst system, either before or after use, with an aromatic compound.

BACKGROUND OF THE INVENTION

[0001] This invention relates to olefin production and olefin productionprocess improvements.

[0002] Olefins, primarily alpha olefins, have many uses. In addition touses as specific chemicals, alpha-olefins, especially mono-1-olefins,are used in polymerization processes either as monomers or comonomers toprepare polyolefins, or polymers. These alpha-olefins usually are usedin a liquid or gas state. Unfortunately, very few efficient processes toselectively produce a specifically desired alpha-olefin are known.

SUMMARY OF THE INVENTION

[0003] Accordingly, it is an object of this invention to provide animproved olefin production process.

[0004] It is another object of this invention to provide an olefinproduction process which will provide high purity 1-hexene.

[0005] It is a further object of this invention to provide an olefinproduction process which can be used in conjunction with other processesthat utilize trimerization reaction reactants and/or reaction products.

[0006] In accordance with this invention, a process is provided totrimerize olefins comprising, in combination a) a reactor, b) at leastone inlet line into said reactor for olefin reactant and catalystsystem, c) effluent lines from said reactor for trimerization reactionproducts, and d) at least one separator to separate desiredtrimerization reaction products; wherein said catalyst system comprisesa chromium source, a pyrrole-containing compound and a metal alkyl.

[0007] In accordance with another embodiment of this invention, aprocess is provided to trimerize ethylene comprising, in combination a)a reactor, b) at least one inlet line into said reactor for ethylenereactant and catalyst system, c) effluent lines from said reactor fortrimerization reaction products, and d) at least one separator toseparate desired 1-hexene reaction product; wherein said catalyst systemcomprises a chromium source, a pyrrole-containing compound, a metalalkyl, and optionally a halide source.

[0008] In accordance with yet another embodiment of this invention, aprocess is provided to trimerize olefins consisting essentially of, incombination a) a reactor, b) at least one inlet line into said reactorfor olefin reactant and catalyst system, c) effluent lines from saidreactor for trimerization reaction products, and d) at least oneseparator to separate desired trimerization reaction products; whereinsaid catalyst system comprises a chromium source, a pyrrole-containingcompound and a metal alkyl.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the drawings, forming a part hereof, wherein like referencecharacters denote like parts in the various figures, FIG. 1 is aschematic representation of one embodiment of an olein trimerizationprocess using four separators, wherein two of said separators are usedfollowing olefin removal. FIG. 2 is a schematic representation ofanother embodiment of an olefin trimerization process using oneseparator after olefin removal. FIG. 3 is a schematic representation ofa further embodiment of an olefin trimerization process using asolventless trimerization reaction system. FIG. 4 is a schematicrepresentation of yet a further embodiment of an olefin trimerizationprocess wherein reactant and trimerized product(s) are sent directly toan olefin polymerization unit. FIG. 5 is a schematic representation ofstill another embodiment of an olefin trimerization process whereincatalyst system and reactor heavies are removed after a separationsequence; other embodiments, such as, for example, include use of twocolumns to separate trimerized product(s), as in FIG. 1, or asolventless system, as in FIG. 3, can be employed as variations. FIG. 6is a schematic representation of yet another embodiment of an olefintrimerization process wherein catalyst system and reactor heaviesstream(s) can undergo further product separation. While these drawingsdescribe embodiments of the invention for the purpose of illustration,the invention is not to be construed as limited by the drawings but thedrawings are intended to cover all changes and modifications within thespirit and scope thereof.

DETAILED DESCRIPTION OF THE INVENTION Catalyst Systems

[0010] Catalyst systems useful in accordance with this inventioncomprise a chromium source, a pyrrole-containing compound and a metalalkyl, all of which have been contacted and/or reacted in the presenceof an unsaturated hydrocarbon. Optionally, these catalyst systems can besupported on an inorganic oxide support. These catalyst systems areespecially useful for the dimerization and trimerization of olefins,such as, for example, trimerization of ethylene to 1-hexene.

[0011] The chromium source can be one or more organic or inorganiccompounds, wherein the chromium oxidation state is from 0 to 6.Generally, the chromium source will have a formula of CrX_(n), wherein Xcan be the same or different and can be any organic or inorganicradical, and n is an integer from 1 to 6. Exemplary organic radicals canhave from about 1 to about 20 carbon atoms per radical, and are selectedfrom the group consisting of alkyl, alkoxy, ester, ketone, and/or amidoradicals. The organic radicals can be straight-chained or branched,cyclic or acyclic, aromatic or aliphatic, can be made of mixedaliphatic, aromatic, and/or cycloaliphatic groups. Exemplary inorganicradicals include, but are not limited to halides, sulfates, and/oroxides.

[0012] Preferably, the chromium source is a chromium(II)- and/orchromium(III)-containing compound which can yield a catalyst system withimproved trimerization activity. Most preferably, the chromium source isa chromium(III) compound because of ease of use, availability, andenhanced catalyst system activity. Exemplary chromium(III) compoundsinclude, but are not limited to, chromium carboxylates, chromiumnaphthenates, chromium halides, chromium pyrrolides, and/or chromiumdionates. Specific exemplary chromium(III) compounds include, but arenot limited to, chromium(III) 2,2,6,6,-tetramethylheptanedionate[Cr(TMHD)₃], chromium(III) 2-ethylhexanoate [Cr(EH)₃, also referred toas chromium(III) tris(2-ethylhexanoate),] chromium(III) naphthenate[Cr(NP)₃], chromium(III) chloride, chromic bromide, chromic fluoride,chromium(III) acetylacetonate, chromium(III) acetate, chromium(III)butyrate, chromium(III) neopentanoate, chromium(III) laurate,chromium(III) stearate, chromium (III) pyrrolides and/or chromium(III)oxalate.

[0013] Specific exemplary chromium(II) compounds include, but are notlimited to, chromous bromide, chromous fluoride, chromous chloride,chromium(II) bis(2-ethylhexanoate), chromium(II) acetate, chromium(II)butyrate, chromium(II) neopentanoate, chromium(II) laurate, chromium(II)stearate, chromium(II) oxalate and/or chromium(II) pyrrolides.

[0014] The pyrrole-containing compound can be any pyrrole-containingcompound, or pyrrolide, that will react with a chromium source to form achromium pyrrolide complex. As used in this disclosure, the term“pyrrole-containing compound” refers to hydrogen pyrrolide, i.e.,pyrrole (C₄H₅N), derivatives of hydrogen pyrrolide, substitutedpyrrolides, as well as metal pyrrolide complexes. A “pyrrolide” isdefined as a compound comprising a 5-membered, nitrogen-containingheterocycle, such as for example, pyrrole, derivatives of pyrrole, andmixtures thereof. Broadly, the pyrrole-containing compound can bepyrrole and/or any heteroleptic or homoleptic metal complex or salt,containing a pyrrolide radical, or ligand. The pyrrole-containingcompound can be either affirmatively added to the reaction, or generatedin-situ.

[0015] Generally, the pyrrole-containing compound will have from about 4to about 20 carbon atoms per molecule. Exemplary pyrrolides are selectedfrom the group consisting of hydrogen pyrrolide (pyrrole), lithiumpyrrolide, sodium pyrrolide, potassium pyrrolide, cesium pyrrolide,and/or the salts of substituted pyrrolides, because of high reactivityand activity with the other reactants. Examples of substitutedpyrrolides include, but are not limited to, pyrrole-2-carboxylic acid,2-acetylpyrrole, pyrrole-2-carboxyaldehyde, tetrahydroindole,2,5-dimethylpyrrole, 2,4-dimethyl-3-ethylpyrrole,3-acetyl-2,4-dimethylpyrrole,ethyl-2,4-dimethyl-5-(ethoxycarbonyl)-3-pyrrole-proprionate,ethyl-3,5-dimethyl-2-pyrrolecarboxylate, and mixtures thereof. When thepyrrole-containing compound contains chromium, the resultant chromiumcompound can be called a chromium pyrrolide.

[0016] The most preferred pyrrole-containing compounds used in atrimerization catalyst system are selected from the group consisting ofhydrogen pyrrolide, i.e., pyrrole (C₄H₅N), 2,5-dimethylpyrrole and/orchromium pyrrolides because of enhanced trimerization activity.Optionally, for ease of use, a chromium pyrrolide can provide both thechromium source and the pyrrole-containing compound. As used in thisdisclosure, when a chromium pyrrolide is used to form a catalyst system,a chromium pyrrolide is considered to provide both the chromium sourceand the pyrrole-containing compound. While all pyrrole-containingcompounds can produce catalyst systems with high activity andproductivity, use of pyrrole and/or 2,5-dimethylpyrrole can produce acatalyst system with enhanced activity and selectivity to a desiredproduct(s).

[0017] The metal alkyl can be any heteroleptic or homoleptic metal alkylcompound. One or more metal alkyls can be used. The alkyl ligand(s) onthe metal can be aliphatic and/or aromatic. Preferably, the alkylligand(s) are any saturated or unsaturated aliphatic radical. The metalalkyl can have any number of carbon atoms. However, due to commercialavailability and ease of use, the metal alkyl will usually comprise lessthan about 70 carbon atoms per metal alkyl molecule and preferably lessthan about 20 carbon atoms per molecule. Exemplary metal alkyls include,but are not limited to, alkylaluminum compounds, alkylboron compounds,alkyl magnesium compounds, alkyl zinc compounds and/or alkyl lithiumcompounds. Exemplary metal alkyls include, but are not limited to,n-butyl lithium, s-butyllithium, t-butyllithium, diethylmagnesium,diethylzinc, triethylaluminum, trimethylaluminum, triisobutylalumium,and mixtures thereof.

[0018] Preferably, the metal alkyl is selected from the group consistingof non-hydrolyzed, i.e., not pre-contacted with water, alkylaluminumcompounds, derivatives of alkylaluminum compounds, halogenatedalkylaluminum compounds, and mixtures thereof for improved productselectivity, as well as improved catalyst system reactivity, activity,and/or productivity. The use of hydrolyzed metal alkyls can result indecreased olefin, i.e., liquids, production and increased polymer, i.e.,solids, production.

[0019] Most preferably, the metal alkyl is a non-hydrolyzedalkylaluminum compound, expressed by the general formulae AlR₃, AlR₂X,AlRX₂, AlR₂OR, AlRXOR, and/or Al₂R₃X₃, wherein R is an alkyl group and Xis a halogen atom. Exemplary compounds include, but are not limited to,triethylaluminum, tripropylaluminum, tributylaluminum, diethylaluminumchloride, diethylaluminum bromide, diethylaluminum ethoxide,diethylaluminum phenoxide, ethylaluminum dichloride, ethylaluminumsesquichloride, and mixtures thereof for best catalyst system activityand product selectivity. The most preferred alkylaluminum compound istriethylaluminum, for best results in catalyst system activity andproduct selectivity.

[0020] Usually, contacting and/or reacting of the chromium source,pyrrole-containing compound and a metal alkyl is done in an unsaturatedhydrocarbon and can be done in any manner known in the art. For example,a pyrrole-containing compound can be contacted with a chromium sourceand then with a metal alkyl. Optionally, a pyrrole-containing compoundcan be contacted with a metal alkyl and then with a chromium source.Numerous other contacting procedures can be used, such as for example,contacting all catalyst system components in the trimerization reactor.

[0021] The unsaturated hydrocarbon can be any aromatic or aliphatichydrocarbon, in a gas, liquid or solid state. Preferably, to effectthorough contacting of the chromium source, pyrrole-containing compound,and metal alkyl, the unsaturated hydrocarbon will be in a liquid state.The unsaturated hydrocarbon can have any number of carbon atoms permolecule. Usually, the unsaturated hydrocarbon will comprise less thanabout 70 carbon atoms per molecule, and preferably, less than about 20carbon atoms per molecule, due to commercial availability and ease ofuse. Exemplary unsaturated, aliphatic hydrocarbon compounds include, butare not limited to, ethylene, 1-hexene, 1,3-butadiene, and mixturesthereof. The most preferred unsaturated aliphatic hydrocarbon compoundis 1-hexene, because of elimination of catalyst system preparation stepsand 1-hexene can be a reaction product. Exemplary unsaturated aromatichydrocarbons include, but are not limited to, toluene, benzene, xylene,ethylbenzene, mesitylene, hexamethylbenzene, and mixtures thereof.Unsaturated, aromatic hydrocarbons are preferred in order to improvecatalyst system stability, as well as produce a highly active andselective catalyst system. The most preferred unsaturated aromatichydrocarbon is selected from the group consisting of toluene andethylbenzene, with ethylbenzene most preferred for best catalyst systemactivity and product selectivity, as well as ease of use.

[0022] Optionally, and preferably, a halide source is also present inthe catalyst system composition. The presence of a halide source in thecatalyst system composition can increase catalyst system activity andproductivity, as well as increase product selectivity. Exemplary halidesinclude, but are not limited to fluoride, chloride, bromide, and/oriodide. Due to ease of use and availability, chloride is the preferredhalide. Based on improved activity, productivity, and/or selectivity,bromide is the most preferred halide.

[0023] The halide source can be any compound containing a halogen.Exemplary compounds include, but are not limited to, compounds with ageneral formula of R_(m)X_(n), wherein R can be any organic and/orinorganic radical, X can be a halide, selected from the group consistingof fluoride, chloride, bromide, and/or iodide, and m+n can be any numbergreater than 0. If R is an organic radical, preferably R has from about1 to about 70 carbon atoms per radical and, most preferably from 1 to 20carbon atoms per radical, for best compatibility and catalyst systemactivity. If R is an inorganic radical, preferably R is selected fromthe group consisting of aluminum, silicon, germanium, hydrogen, boron,lithium, tin, gallium, indium, lead, and mixtures thereof. Specificexemplary compounds include, but are not limited to, methylene chloride,chloroform, benzylchloride, silicon tetrachloride, tin(II) chloride,tin(IV) chloride, germanium tetrachloride, boron trichloride, aluminumtribromide, aluminum trichloride, 1,4-di-bromobutane, and/or1-bromobutane. Most preferably, the halide source is selected from thegroup consisting of tin (IV) halides, germanium halides, and mixturesthereof.

[0024] Furthermore, the chromium source, the metal alkyl and/orunsaturated hydrocarbon can contain and provide a halide to the reactionmixture. Preferably, if a halide is present, the halide source is analkylaluminum halide and is used in conjunction with alkylaluminumcompounds due to ease of use and compatibility, as well as improvedcatalyst system activity and product selectivity. Exemplaryalkylaluminum halides include, but are not limited to,diisobutylaluminum chloride, diethylaluminum chloride, ethylaluminumsesquichloride, ethylaluminum dichloride, diethylaluminum bromide,diethylaluminum iodide, and mixtures thereof.

[0025] It should be recognized, however, that the reaction mixturecomprising a chromium source, pyrrole-containing compound, metal alkyl,unsaturated hydrocarbon and optionally a halide can contain additionalcomponents which do not adversely affect and can enhance the resultantcatalyst system.

Reactants

[0026] Trimerization, as used in this disclosure, is defined as thecombination of any two, three, or more olefins, wherein the number ofolefin, i.e., carbon-carbon double bonds is reduced by two. Reactantsapplicable for use in the trimerization process of this invention areolefinic compounds which can a) self-react, i.e., trimerize, to giveuseful products such as, for example, the self reaction of ethylene cangive 1-hexene and the self-reaction of 1,3-butadiene can give1,5-cyclooctadiene; and/or b) olefinic compounds which can react withother olefinic compounds, i.e., co-trimerize, to give useful productssuch as, for example, co-trimerization of ethylene plus hexene can give1-decene and/or 1-tetradecene, co-trimerization of ethylene and 1-butenecan give 1-octene, co-trimerization of 1-decene and ethylene can give1-tetradecene and/or 1-docosene. For example, the number of olein bondsin the combination of three ethylene units is reduced by two, to oneolefin bond, in 1-hexene. In another example, the number of olefin bondsin the combination of two 1,3-butadiene units, is reduced by two, to twoolefin bonds in 1,5-cyclooctadiene. As used herein, the term“timerization” is intended to include dimerization of diolefins, as wellas “co-trimerization”, both as defined above.

[0027] Suitable trimerizable olefin compounds are those compounds havingfrom about 2 to about 30 carbon atoms per molecule and having at leastone olefinic double bond. Exemplary mono-1-olefin compounds include, butare not limited to acyclic cyclic olefins such as, for example,ethylene, propylene, 1-butene, 2-butene isobutylene, 1-pentene,2-pentene, 1-hexene, 2-hexene, 3-hexene, 1-heptene, 2-heptene,3-heptene, the four normal octenes, the four normal nonenes, andmixtures of any two or more thereof. Exemplary diolefin compoundsinclude, but are not limited to, 1,3-butadiene, 1,4-pentadiene, and1,5-hexadiene. If branched and/or cyclic olefins are used as reactants,while not wishing to be bound by theory, it is believed that sterichindrance could hinder the trimerization process. Therefore, the branchand/or cyclic portion(s) of the olefin preferably should be distant fromthe carbon-carbon double bond.

[0028] Catalyst systems produced in accordance with this inventionpreferably are employed as trimerization catalyst systems.

Products

[0029] The olefinic products of this invention have established utilityin a wide variety of applications, such as, for example, as monomers foruse in the preparation of homopolymers, copolymers, and/or terpolymers.The olefinic products of this invention can have from about 6 to about100 carbon atoms per molecule. As discussed previously, trimerization ofethylene can yield hexenes, preferably 1-hexene. Trimerization ofethylene and 1-hexene can produce decenes, preferably 1-decene.Trimerization of 1,3-butadiene can produce 1,5-cyclooctadiene.

DRAWINGS

[0030] A further understanding of some of the aspects of this inventioncan be found by referring to the attached schematic flow diagrams, incombination with the following descriptions. Various additional pumps,valves, heaters, coolers and other conventional equipment necessary forthe practice of this invention will be familiar to one skilled in theart. Said additional equipment has been omitted from the drawings forthe sake of clarity. The descriptions of the drawings provide one methodfor operating the process. However, it is understood that while thesedrawings are general representations of the process, minor changes canbe made in adapting the drawings to the various conditions within thescope of the invention. It is also understood that numerical referencesin the drawings are consistent throughout the drawings. For example,inlet line 1, an olefin and optionally hydrogen inlet line, is an olefinand optionally hydrogen inlet line in all drawings.

[0031] As used in this disclosure, “olefin feed” refers to compoundsmore fully defined in the “Reactant” portion of this disclosure, suchas, for example, ethylene, propylene, and/or 1-hexene. “Solvent” refersto a diluent or medium in which the trimerization process occurs;however, by no means is the solvent necessarily an inert material; it ispossible that the solvent can contribute to a trimerization reactionprocess. Exemplary solvents include, but are not limited to,cyclohexane, methylcyclohexane, isobutane, 1-hexene, and mixtures of twoor more thereof. “Reactor effluent” refers to all components that can bepresent in and can be removed from a trimerization reactor, including,but not limited to, unreacted olefin, catalyst system, trimerizationproduct(s) and/or reaction co-product(s), also referred to as reactionby-product(s). “Catalyst kill” refers to those compounds which candeactivate, either partially or completely, catalyst system used in thetrimerization process. “Heavies” refers to reaction co-product(s) whichhave a higher molecular weight than olefin reactants and/or the desiredtrimerization reaction product(s), and include higher olefinic products,such as, for example decenes and tetradecenes, as well as polymericproducts.

[0032] Referring to FIG. 1, olefin feed, and optionally hydrogen, is fedthrough inlet line 1 into trimerization reactor 4. Inlet line 2introduces catalyst system and optionally, solvent into trimerizationreactor 4. Inlet line 3, an optional embodiment of the invention, cansupply olefin feed from a second source, such as, for example anethylene effluent, or discharge, stream from a polyethylenepolymerization production facility. Trimerization reactor effluentcomprising trimerized product(s), reaction co-product(s), unreactedolefin, catalyst system, and other reactor components is removed viaeffluent line 6. Catalyst system deactivation, i.e., “kill”, components,if desired are fed via inlet line 5 into effluent line 6. It should benoted that lines 1, 2, 3, and 6 can be located anywhere on trimerizationreactor 4. However, the location of lines 1, 2, and 3 must allow olefinfeed stream to thoroughly contact catalyst system from line 2 intrimerization reactor 4. Filter 7 is an optional embodiment of theinvention which can remove particulates, such as, for example, catalystfines and undesirable polymeric products, from effluent line 6. Forexample, if the reactor effluent stream in effluent line 6 is maintainedat a higher temperature, fewer particulates, such as, for exampleparticulates resulting from undesirable polymer product(s), can form andfilter 7 may not be necessary. While not wishing to be bound by theory,it is believed that higher reactor and line temperatures can inhibitsolidification of undesirable polymer particles, i.e., highertemperatures can keep undesirable polymer particles from precipitating.However, if the reactor effluent stream in effluent line 6 is allowed tocool and particulates can form, filter 7 can be used. Line 8 can beeither filter 7 effluent or a continuation of effluent line 6 and line 8comprises little or no particulates. Inlet line 9 is a further optionalembodiment of the invention and can include a stream of heavies to beseparated, such as, for example a discharge effluent stream from apolyethylene production plant. Separator 10 separates catalyst systemand other heavies from lighter olefins. Effluent line 12 is an effluentstream comprising catalyst system and other heavy olefins from separator10. Effluent line 11 also is an effluent stream from separator 10 andcan be used to recover light olefins, including trimerized products.Separator 13 can be used to separate trimerized products from olefinreactants via effluent line 14 and solvent via effluent line 15.Separator 16 can be used to separate desired trimerization product(s)via effluent line 17 from trimerization reaction solvent via effluentline 18. Separator 19 can be used to separate trimerization reactionsolvent via effluent line 20 for reuse or recycle from other componentswhich can be removed via effluent line 21.

[0033] Referring now to FIG. 2, another embodiment of the invention,wherein like numbers represent like components, separator 22 and lines23, 24, and 25 are added. Separator 22 can be used to separatetrimerization product(s) via effluent line 23 from trimerizationreaction solvent via effluent line 24 and any other remaining reactioncomponents via effluent line 25.

[0034] Referring now to FIG. 3, another embodiment of the invention,wherein like numbers represent like components and wherein a solvent isnot used during the trimerization process. Therefore, separator 26 isused to separate trimerization product(s) via effluent line 27 from allother remaining components removed via effluent line 28.

[0035] Referring now to FIG. 4, another embodiment of the inventionwherein like numbers represent like components, separator 29 is used toseparate olefin feed and trimerization product(s) via effluent line 30.If desired, olefin feed and trimerization product(s) can be fed directlyto an olefin polymerization unit where an olefin feed and trimerizedproduct(s) are polymerized to form a copolymer, such as, or example anethylene hexene copolymer. Solvent, if present in trimerization reactor4, can be removed from separator 29 via effluent line 31. Effluent line32 removes excess and/or deactivated catalyst system and other heavieswhich can be produced during the trimerization reaction.

[0036] Referring to FIG. 5, again like numbers represent like systemcomponents, separator 33 is used to recover any unreacted olefin feedvia effluent line 34. Effluent line 35 carries all non-recovered olefinproducts to separator 37. Inlet line 36 is similar to inlet line 9 inprevious drawings wherein a stream of heavies from another location,such as, for example a polyethylene plant, is added for separation.Separator 37 can be used to separate trimerization product(s) viaeffluent line 38, solvent via effluent line 39, and catalyst and otherproducts via effluent line 40.

[0037] Referring now to FIG. 6, another embodiment of the invention,wherein like numbers represent like components and wherein a catalystsystem and heavies effluent line can be fed to separator 41 to separatetrimerization reaction by-products, such as decenes via effluent line 42from other reactor effluent components via effluent line 43, such as,for example catalyst system, polymer particulates, other higher olefinicby-products, including some decenes. It should be noted that some of thedecenes must be kept in effluent line 43 in order to maintainflowability of catalyst system effluent and/or discharge products andpossible polymer particulates, if not removed previously in filter 7.Decenes removed via effluent line 42 can be recovered or routed foradditional use, such as hydrogenation to commercially useful productssuch as Soltrol® 100.

[0038] Note that the invention is not limited only to the embodimentsspecifically shown in the figures. For example FIG. 5 shows oneseparator 37 after an olefin removal separator 33. Other variants, suchas using two separator columns to separate trimerized product(s) andsolvent, such as in FIG. 1 with separator 16 and separator 19, can beused or solvent removal may not be necessary, as shown in FIG. 3 withseparator 26.

Reaction Conditions

[0039] Reaction products, i.e., olefin trimers as disclosed in thisspecification, can be prepared with the disclosed catalyst systems bysolution reaction, slurry reaction, and/or gas phase reaction techniquesusing conventional equipment and contacting processes. Contacting of theolefin feed with a catalyst system can be effected by any manner knownin the art. One convenient method is to suspend the catalyst system in asolvent, i.e., diluent or medium, and to agitate the mixture to maintaina uniform catalyst system concentration throughout the reaction mixtureand/or maintain the catalyst system in solution throughout thetrimerization process. Other known contacting methods can also beemployed.

[0040] A trimerization process can be carried out in an inert solvent,such as a paraffin, cycloparaffin, or aromatic hydrocarbon. Exemplaryreactor diluents include, but are not limited to, isobutane, cyclohexaneand methylcyclohexane. Isobutane can be used to improve processcompatibility with other known olefin production processes. However, ahomogenous trimerization catalyst system can be more soluble incyclohexane. Therefore, a preferred solvent for a homogeneous catalyzedtrimerization process is cyclohexane.

[0041] Alternatively, a “solventless” reaction system can be used. In asolventless system, reaction product can be the reactor “solvent” ordiluent. For example, if ethylene is trimerized to 1-hexene, 1-hexenecan be used in the reactor as a solvent, or diluent. A solventlessreaction system is preferred in that fewer separation steps can be usedfollowing completion of the trimerization reaction.

[0042] Reaction temperatures and pressures can be any temperature andpressure which can trimerize the olefin reactants. When the reactant ispredominately ethylene, a temperature in the range of about 0° to about300° C. (about 32° to about 575° F.) generally can be used. Preferably,when the reactant is predominately ethylene, a temperature in the rangeof about 60° to about 275° C. (about 140° to about 530° F.) is employed.Most preferably, reactor temperature is within a range of 110° to 125°C. (235° to 255° F.). Reactor temperatures that are too low can causepolymeric products to precipitate out of the process can decreaseproduct selectivity by increasing the production of polymeric products.Reactor temperatures that are too high can decrease catalyst systemactivity, negatively affect reaction selectivity and can causedecomposition of the catalyst system and reaction products. However,reactor temperature range s can vary if other solvents are used in thetrimerization process.

[0043] Generally, reaction pressures are within a range of aboutatmospheric to about 2500 psig. Selection of reaction pressure dependson the solvent, or diluent, used in the reactor. Preferably, when usinga diluent other than 1-hexene, reaction pressures within a range ofabout atmospheric to about 1500 psig and most preferably, within a rangeof 600 to 1000 psig are employed. Preferably, when using 1-hexene as thediluent, reaction pressures within a range of about atmospheric to about2000 psig and most preferably, within a range of 1100 to 1600 psig areemployed. Too low of a reaction pressure can result in low catalystsystem activity.

[0044] Optionally, hydrogen can be added to the reactor to enhanceproduct selectivity, i.e., reduce formation of polymeric products.

[0045] A further understanding of the present invention and itsadvantages also will be provided by reference to the following examples.

EXAMPLES Example 1

[0046] This example shows different methods of preparing trimerizationcatalyst systems and the trimerization results. Runs 101-106 demonstratecatalyst system preparation outside of the trimerization reactor andfeeding catalyst system into the trimerization reactor. Runs 107-109demonstrate a catalyst system preparation method inside thetrimerization reactor. Runs 110-112 demonstrate another catalyst systempreparation method inside the trimerization reactor. All catalyst systempreparation was carried out under an inert atmosphere (nitrogen orhelium) using standard Schlenk techniques, if applicable. All solvents,or diluents, were dried over mole sieves/alumina and purged withnitrogen before use. The components used to prepare the catalyst systemsand the molar ratios of chromium to other catalyst system components arelisted in Table 1.

[0047] Catalyst systems used in Runs 101-106 were prepared by dissolvingchromium tris(2-ethylhexanoate) [Cr(EH)₃) in toluene or ethylbenzene (40ml/g Cr(EH)₃). In a separate container, triethylaluminum (TEA) and achloride source were mixed together. 2,5-Dimethylpyrrole (DMP) was addedto either the Cr(EH)₃ solution or the aluminum alkyl-chloride source.The chromium mixture, either with or without DMP, depending on thepreparation method selected above, was added to the aluminum mixture andthe resulting brown-yellow solution was stirred for a time within arange of 10 minutes to one (1) hour. The resulting solution then wasfiltered through a celite frit and was diluted to the desiredconcentration.

[0048] Catalyst systems used in Runs 107-109 were prepared by dissolvingCr(EH)₃ in cyclohexane and diluting to the desired concentration withadditional cyclohexane. This solution was charged to a catalyst feedtank to the reactor. TEA and chloride sources were mixed together in 200ml of cyclohexane. DMP was added to the aluminum alkyl/chloride sourceand allowed to react for 5 minutes. This solution, along with thesolvent for that particular run, was charged to a solvent feed tank tothe reactor. Thus, the aluminum alkyl/chloride source/DMP mixture wasfed to the reactor in the same stream as the reactor solvent, butseparately from the chromium source.

[0049] Catalyst systems used in Runs 110-112 were prepared by dissolvingCr(EH)₃ in cyclohexane and diluting to the desired concentration withadditional cyclohexane. This solution was charged to a catalyst feedtank to the reactor. TEA and chloride sources were mixed together in 100ml of cyclohexane. DMP was added to the aluminum alkyl/chloride sourceand allowed to react for 5 minutes. The resulting aluminumalkyl/chloride source/DMP solution was diluted to the desiredconcentration with additional cyclohexane and then charged an aluminumfeed tank to the reactor. Thus, the aluminum alkyl/chloride source/DMPmixture was fed to the reactor in a separate stream from either thereactor solvent or the chromium source.

[0050] All trimerization reactions disclosed in Runs 101-112 can beconsidered continuous feed reactions, i.e., not batch reactions. Thefeed rates and temperatures of all Runs are given in Table 2. Reactorvolume in Runs 101, 105 and 110-112 was 0.264 gallons; reactor volume inall other Runs was one (1) gallon. Reactor pressure in Run 102 was 1465psia; reactor pressure in all other Runs was 800 psia. The temperatureand pressure of the reactor were continuously controlled at the desiredvalues. Reactor temperature was controlled by an internal coiled pipe.Each Run sequence was started by turning on a solvent pump to fill theautoclave reactor and heating the reactor to the desired temperature.The reactor was purged with the solvent shown in Table 2 for 30 minutes.Additional process conditions are given in Table 1.

[0051] In Runs 101-107, catalyst system was fed to the reactor at doublethe desired rate for 30 minutes prior to the introduction of ethyleneand then reduced to the desired feed rate. In Runs 101 and 103-106,solvent feed continued during catalyst system feed and ethylene/hydrogenmixture feed. In Run 102, 1-hexene was fed with catalyst system untilthe addition of the ethylene/hydrogen mixture; 1-hexene feed was stoppedwhen the ethylene/hydrogen mixture feed began.

[0052] In Runs 107-109, two different reactor inlets simultaneously feda) a catalyst system portion comprising a Cr(EH)₃ solution and b)solvent and another catalyst system portion comprising an aluminumalkyl/chloride source/DMP solution.

[0053] In Runs 110-112, three different reactor inlets simultaneouslyfed a) a catalyst system portion comprising a Cr(EH)₃ solution, b)another catalyst system portion comprising an aluminum alkyl/chloridesource/DMP solution, and c) solvent.

[0054] Upon exit from the reactor, the catalyst/product solution streamwas deactivated with an alcohol, cooled and filtered in a pressurevessel through a steel sponge filter material to remove polymericsolids. The product stream was taken to a product storage tank.

[0055] Each reaction was monitored for 6 hours. On-line samples werecollected once every hour and analyzed by gas chromatography todetermine reactor effluent composition. Product analyses are given inTable 2. TABLE 1 Catalyst Components and Process Conditions Solvent H₂Reactor Catalyst Catalyst Al Feed C₂ = Feed Feed Feed Moles/mole CrChloride Temp, Concent. Feed Rate, Rate, Rate, Rate, Rate, Run DMP TEAChloride Source Solvent ° C. MgCr/ml ml/hr ml/hr g/hr gallons/hr l/hr101 3.0 11.0 8.0 DEAC Isobutane 100 0.35 45 — 275 0.60 4.40 102 1.8 9.02.5 EADC l-Hexene 115 0.50 30 — 1570 0.00 15.7 103 1.8 6.5 5.0 DEACCyclohexane 115 0.80 30 — 1430 1.20 5.20 104 3.0 11.0 8.0 DEACCyclohexane 115 0.17 30 — 1450 1.35 4.10 105 3.0 11.0 8.0 DEAC n-Heptane120 0.25 30 — 560 0.50 3.10 106 3.0 11.0 8.0 DEAC Methyl- 128 1.01 45 —1640 1.35 8.20 cyclohexane In-situ —Al in solvent 107 3.0 11.0 8.0 DEACCyclohexane 115 0.33 30 — 1430 1.20 5.20 108 3.0 19.0 1.3 C2C16Cyclohexane 115 0.33 30 — 1430 1.20 5.20 109 16.0 50.0 63.0 DEACCyclohexane 115 0.04 30 — 1430 1.20 5.20 In-situ —Al in Tank 110 3.011.0 8.0 DEAC Cyclohexane 120 .29 25 25 550 0.40 3.10 111 3.0 11.0 8.0DEAC Cyclohexane 120 .29 25 25 550 0.40 3.10 112 3.0 11.0 8.0 DEACCyclohexane 120 .29 25 25 550 0.40 3.10

[0056] TABLE 2 Product Analysis (weight percents) % Productivity,Productivity, % % Internal Hexene % % % Ethylene Polymer g olefin/g golefin/g Run Butenes l-Hexene Hexenes Purity, % Octenes DecenesConversion Produced, g Cr-hr Metals - hr 101 <0.1 93.7 1.4 98.6 0.3 4.642.3 0.4 7000 640 102 0.4 88.8 0.8 99.1 0.5 8.8 78.1 2.9 71800 10300 1030.1 84.5 0.7 99.2 0.2 13.3 86.6 2.4 43400 6220 104 0.1 94.1 0.4 99.6 0.35.1 68.0 1.6 185000 17000 105 0.1 91.8 0.8 99.1 0.3 6.7 72.0 0.4 493004540 106 0.3 85.0 1.5 98.3 0.4 11.9 83.2 1.1 25600 2350 107 0.1 92.1 0.499.6 0.3 6.8 75.9 2.5 101000 9300 108 0.2 79.9 1.5 98.2 0.4 16.4 89.91.1 104000 9550 109 0.1 96.2 0.6 99.6 0.3 3.1 47.2 1.0 533000 8940 1100.2 91.5 0.6 99.3 <0.1 7.2 76.5 0.1 52300 4810 111 0.2 93.0 0.6 99.3 0.15.6 74.9 0.3 52000 4790 112 0.2 92.5 0.7 99.3 0.2 6.1 74.6 0.1 515004740

Example 2

[0057] These examples demonstrate the process of trimerizing ethylene tomake 1-hexene and the separation steps necessary to produce the desiredproduct purity.

[0058] Greater than 98.5% purity 1-hexene was produced in Runs 201-203in the following manner. Ethylene and catalyst system were fed to areactor in the presence of a diluent/solvent. The reactor effluent wasstripped of ethylene in column 1. Subsequently, 1-hexene product wasremoved from the diluent/solvent, spent catalyst, and other heavierco-products in column 2. Finally, spent catalyst and other heavies wereremoved from the diluent/solvent in column 3. The diluent/solvent thenwas returned to the reactor.

[0059] The reactor was liquid full and had a volume of 10 gallons.Columns 1, 2, and 3 were packed towers. The diluent/solvent wasmethylcyclohexane. The reactor pressure used was 800 psig (5516 Kpa).

Run 201

[0060] The catalyst system was prepared in the same manner as describedin Example 1.

[0061] To produce 1-hexene, ethylene and methylcyclohexane were fed tothe reactor at a rate of 34.9 lbs/hr and 66.7 lbs/hr average,respectively. Hydrogen was added at an average rate of 3.4 standardcubic feet per hour. Catalyst was metered into the reactor at an averagerate of 256 ml/hr. The reactor temperature was 244 F (118 C).

[0062] At the conditions specified, 1-hexene product was removed fromcolumn 2 at an average rate of 24.9 lbs/hr. Product purity was 98.8weight percent 1-hexene, with off hexenes being the other majorcomponents. Overall, selectivity of ethylene to 1-hexene was 85.9 weightpercent.

Run 202

[0063] Catalyst system was prepared in the same manner as described inExample 2.

[0064] Ethylene and methylcyclohexane were fed to the reactor at a rateof 49.9 lbs/hr and 118.8 lbs/hr average, respectively. Hydrogen wasadded at an average rate of 4.1 standard cubic feet per hour. Catalystwas metered into the reactor at an average rate of 230 ml/hr. Reactortemperature was 247° F. (120° C.).

[0065] At the conditions specified, 1-hexene product was removed fromcolumn 2 at an average rate of 31.1 lbs/hr. Product purity was 99.1weight percent 1-hexene, with off-hexenes being the other majorcomponents. Overall, selectivity of ethylene to 1-hexene was 92.1 weightpercent.

Run 203

[0066] The catalyst system was prepared in the same manner as describedin Example 1.

[0067] Ethylene and methylcyclohexane were fed to the reactor at a rateof 65.2 lbs/hr and 176.3 lbs/hr average, respectively. Hydrogen wasadded at an average rate of 6.4 standard cubic feet per hour. Catalystwas metered into the reactor at an average rate of 285 ml/hr. Reactortemperature was 264° F. (129° C.).

[0068] At the conditions specified, 1-hexene product was removed fromcolumn 2 at an average rate of 37.7 lbs/hr. Product purity was 99.3weight percent 1-hexene, with off-hexenes being the other majorcomponents. Overall, selectivity of ethylene to 1-hexene was 94.4 weightpercent.

Example 3

[0069] This example shows that coproducts of the trimerization reaction,which include decenes, can be hydrogenated and incorporated intocommercially useful and available solvents, such as Soltrol® 1100.Soltrol® 100 is a registered trademark of Phillips Petroleum Company andis a mix of C₉-C₁₁ isoparaffins. One embodiment of such a hydrogenationprocess is shown in FIG. 6.

[0070] Catalyst activation and hydrotreatment were done in a downflow2′×¾″ OD fixed-bed reactor. The reactor was charged with 15 ml of 3 mmglass beads, 20 ml of commercially available Englehard Ni5254, lot HE 38hydrogenation catalyst, and topped with Alcoa alumina A201. Heat controlwas accomplished in a 3-zone tube furnace. Catalyst activation was doneat 343° C. with 300 cc/min of hydrogen (H₂, 99.9%) for three hours priorto hydrogenation of a decene isomer fraction of the trimerizationreaction co-product.

[0071] A decene isomer fraction of the trimerization reactionco-product, was hydrotreated as it was feed to the reactor by a syringepump. Hydrogen was provided to the top of the reactor through acalibrated mass flow controller at 100 cc/min. Total pressure of 400psig to the system was maintained at the reactor exit by a Mooreregulator. Samples were periodically analyzed for bromine number andanalyzed by GC and UV.

[0072] Hydrotreatment proceeded smoothly with 100% reduction of thedecene to decane isomers at 1 liquid hourly spaced velocity (LHSV), 150°C., 400 psig hydrogen. However, when the LHSV was raised to 3, 150° C.and 400 psig H₂, total decene isomer conversion dropped to 76%.Increasing the reactor temperature to 200° C. increased conversion to83%. Complete decene isomer conversion resulted again when the 1 LHSV,150° C., 400 psig H₂ conditions were used. As is normal forhydrotreating reactions, a heat rise was noted across the reactor whichwas LHSV dependent. At 1 LHSV, the heat rise was 35° C.; at 3 LHSV theheat rise was 47° C. Conversion results were confirmed by GC, GC/MS andbromine number analysis. The results of these hydrogenations are listedbelow in Table 3. TABLE 3 % Reduction, Reactor H₂ Pressure, Heat Decenesto Run LHSV Temp, ° C. psig Rise, ° C. Decanes 301 1 150 400 35 100 3023 150 400 47 76 303 3 200 400 47 83 304 1 150 400 35 100

[0073] A commercially available Soltrol® 100 sample, that had beenhydrotreated was used to prepare blends stocks with the abovehydrotreated product. Blends of C₁₀/Soltrol® 100 were made in 2, 10, 20,30 and 50 volume percent concentrations to evaluate the compatibility ofthese two products. GC analysis, using a column that separates accordingto boiling points, show that the decane isomers fit into the Soltrol®1100 boiling point range. The Soltrol® 100 purity was not reduced by theaddition of the hydrotreated decene product.

[0074] While this invention has been described in detail for the purposeof illustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

1-11. (Cancelled)
 12. In the selective conversion of olefins to olefintrimerization products a process comprising: a) introducing a feedstockcomprising olefins and hydrogen into a reactor; b) separatelyintroducing a catalyst system comprising a chromium source, apyrrole-containing compound, and a metal alkyl into the reactor, therebycontacting the feedstock and the catalyst system in the reactor; c)maintaining the feedstock and catalyst system in the reactor underconditions to produce a reactor effluent comprising unreacted olefins,olefin trimerization products, catalyst, and heavies; d) transferringreactor effluent comprising unreacted olefins, olefin trimerizationproducts, and heavies from the reactor to a first separator whereincatalyst and heavies are separated from the reactor effluent; e)removing from the first separator a first effluent stream comprising atleast catalyst and heavies; and f) removing from the first separator asecond effluent stream comprising at least unreacted olefins.
 13. Theprocess according to claim 12, wherein the reactor effluent is filteredbefore entering the first separator.
 14. The process according to claim12, wherein catalyst kill is introduced into the reactor effluent. 15.The process according to claim 14, wherein the reactor effluent isfiltered after introduction of the catalyst kill.
 16. The processaccording to claim 12, wherein heavies from a source independent of thereactor effluent are introduced into the reactor effluent beforeintroduction into the first separator.
 17. The process according toclaim 12, wherein an effluent stream comprising olefin and trimerizationproduct is transferred from the first separator to a second separatorwherein the effluent stream is separated into a predominantly olefineffluent stream and a predominantly trimerization product effluentstream.
 18. The process according to claim 17, wherein the predominantlytrimerization product effluent stream is transferred from the secondseparator to a third separator to separate remaining heavies from thepredominantly trimerization product effluent to provide a trimerizationproduct effluent stream.
 19. The process according to claim 12, furthercomprising: treating the first effluent stream by recovering a portionof heavier trimerized product.
 20. The process according to claim 12,wherein diluent is introduced into the reactor along with the catalystsystem.
 21. In the selective conversion of olefins to olefintrimerization products, a process comprising: a) introducing a feedstock comprising olefins and hydrogen into a reactor; b) separatelyintroducing a stream comprising diluent and a catalyst system comprisinga chromium source, a pyrrole-containing compound, and a metal alkyl intothe reactor, thereby contacting diluent, feedstock, and catalyst systemin the reactor; c) maintaining the feedstock and catalyst system in thereactor under conditions to produce a reactor effluent comprisingdiluent, unreacted olefins, olefin trimerization products, catalyst, andheavies; d) transferring reactor effluent comprising diluent, unreactedolefins, olefin trimerization products, and heavies from the reactor toa first separator wherein the reactor effluent is separated into 1)catalyst and heavies, 2) diluent, and 3) unreacted olefin andtrimerization products; e) removing from the first separator apredominantly catalyst and heavies stream; f) removing from the firstseparator a predominantly diluent stream; and g) removing from the firstseparator a predominantly unreacted olefin and trimerization productsstream.
 22. A process for making an olefin trimerization productcomprising: contacting an olefin feedstock with a catalyst systemcomprising a chromium source, a pyrrole-containing compound, and a metalalkyl; maintaining the olefin feedstock and the catalyst system underconditions to produce a reactor effluent comprising the olefintrimerization product and reactor products; and separating the olefintrimerization product from the reactor effluent.
 23. The processaccording to claim 22, wherein the olefin feedstock and the catalystsystem are contacted in a reactor and are introduced therein independentof one another.
 24. The process according to claim 22, wherein thecontacting of the olefin feedstock and the catalyst system is conductedin the presence of hydrogen.
 25. The process according to claim 22,wherein the contacting of the olefin feedstock and the catalyst systemis conducted in the presence of a diluent.
 26. The process according toclaim 25, wherein the diluent is selected from paraffin, cycloparaffin,an aromatic hydrocarbon, isobutane, cyclohexane, methylcyclohexane,isobutene, 1-hexene, or any combination thereof.
 27. The processaccording to claim 22, wherein the catalyst system is present in thereactor effluent and the process further comprises deactivating thecatalyst system in the reactor effluent prior to separating the olefintrimerization product therefrom.
 28. The process according to claim 22,further comprising filtering the reactor effluent prior to separatingthe olefin trimerization product therefrom.
 29. The process according toclaim 22, further comprising: heating the reactor effluent.
 30. Theprocess according to claim 22, further comprising: introducing heaviesfrom a source independent of the reactor effluent into the reactoreffluent; and separating the heavies from the reactor effluent.
 31. Theprocess according to claim 22, wherein the catalyst system is present inthe reactor products and the process further comprises separating thecatalyst system from the reactor products.
 32. The process according toclaim 22, wherein the olefin feedstock comprises an olefinic compoundwhich is self-reacting to trimerize or an olefinic compound which reactswith other olefinic compounds to form a co-trimerization product. 33.The process according to claim 22, wherein the olefin feedstockcomprises one or more olefin compounds having from about 2 to about 30carbon atoms per molecule.
 34. The process according to claim 22,wherein the olefin feedstock and the catalyst system is maintained at atemperature in the range of about 0° C. to about 300° C. (about 32° F.to about 575° F.).
 35. The process according to claim 22, wherein theolefin feedstock and the catalyst system are maintained at a temperaturein the range of about 60° C. to about 275° C. (about 140° F. to about530° F.).
 36. The process according to claim 22, wherein the olefinfeedstock and the catalyst system are maintained at a temperature in therange of about 110° C. to about 125° C. (about 235° F. to about 255°F.).
 37. The process according to claim 22, wherein the olefin feedstockand the catalyst system are maintained at a pressure in the range ofabout atmospheric to about 2500 psig.
 38. The process according to claim22, wherein the olefin feedstock and the catalyst system are maintainedat a pressure in the range of about atmospheric to about 1500 psig. 39.The process according to claim 22, wherein the olefin feedstock and thecatalyst system are maintained at a pressure in the range of about 600psig to about 1000 psig.
 40. The process according to claim 25, whereinthe olefin feedstock and the catalyst system are maintained at apressure in the range of about atmospheric to about 2000 psig when thediluent comprises 1-hexene.
 41. The process according to claim 25,wherein the olefin feedstock and the catalyst system are maintained at apressure in the range of about 1100 psig to about 1600 psig when thediluent comprises 1-hexene.
 42. The process according to claim 22,wherein the catalyst system further comprises an inorganic oxidesupport.
 43. The process according to claim 22, wherein the chromiumsource of the catalyst system comprises one or more organic or inorganicchromium compounds, wherein the chromium oxidation state is from 0 to 6.44. The process according to claim 22, wherein the chromium source ofthe catalyst system comprises a compound having a general formula ofCrX_(n), wherein X is the same or different and is any organic orinorganic radical and n is an integer from 1 to
 6. 45. The processaccording to claim 44, wherein X is an organic radical having from 1 toabout 20 carbon atoms per radical.
 46. The process according to claim44, wherein X is an organic radical selected from alkyl, alkoxy, ester,ketone, amido, or any combination thereof.
 47. The process according toclaim 44, wherein X is an inorganic radical selected from halides,sulfates, oxides, or any combination thereof.
 48. The process accordingto claim 22, wherein said chromium source of the catalyst systemcomprises a chromium (II) compound, chromium (III) compound, or acombination thereof.
 49. The process according to claim 22, wherein thechromium source of the catalyst system comprises a chromium (III)compound selected from chromium carboxylates, chromium naphthenates,chromium halides, chromium pyrrolides, chromium dionates, or anycombination thereof.
 50. The process according to claim 22, wherein thepyrrole-containing compound of the catalyst system is reactable with thechromium source to form a chromium pyrrolide complex.
 51. The processaccording to claim 22, wherein the pyrrole-containing compound of thecatalyst system is a pyrrole, any heteroleptic or homoleptic metalcomplex or salt containing a pyrrolide radical or ligand, or anycombination thereof.
 52. The process according to claim 22, wherein thepyrrole-containing compound is hydrogen pyrrolide (pyrrole), chromiumpyrrolide, lithium pyrrolide, sodium pyrrolide, potassium pyrrolide,cesium pyrrolide, salts of substituted pyrrolides, or any combinationthereof.
 53. The process according to claim 22, wherein the metal alkylof the catalyst system is a heteroleptic metal alkyl compound, ahomoleptic metal alkyl compound, or a combination thereof.
 54. Theprocess according to claim 22, wherein the metal alkyl of the catalystsystem is alkylaluminum compounds, alkylboron compounds, alkyl magnesiumcompounds, alkyl zinc compounds, alkyl lithium compounds, or anycombination thereof.
 55. The process according to claim 22, wherein themetal alkyl of the catalyst system is a non-hydrolyzed alkylaluminumcompound having a general formula of AlR₃, AlR₂X, AlRX₂, AlR₂OR, AlRXOR,Al₂R₃X₃, or any combination thereof, wherein R is an alkyl group and Xis a halogen atom.
 56. The process according to claim 22, wherein thechromium source, the pyrrole-containing compound, and the metal alkylare contacted in the presence of an unsaturated hydrocarbon.
 57. Theprocess according to claim 56, wherein the unsaturated hydrocarbon is anaromatic or aliphatic hydrocarbon in the form of a gas, liquid, orsolid.
 58. The process according to claim 56, wherein the unsaturatedhydrocarbon is ethylene, 1-hexene, 1,3-butadiene, toluene, benzene,xylene, ethylbenzene, mesitylene, hexamethylbenzene, or any combinationthereof.
 59. The process according to claim 22, wherein the catalystsystem further comprises a halide source.
 60. The process according toclaim 59, wherein the halide source has a general formula of R_(m)X_(n),wherein R is an organic or inorganic radical, X is a halide radical, andm+n is a number greater than
 0. 61. The process according to claim 22,wherein the chromium source, the metal alkyl, or both of the catalystsystem comprise a halide.
 62. The process according to claim 56, whereinthe chromium source, the metal alkyl, the unsaturated hydrocarbon, orany combination thereof comprise a halide.